I would say the constant engine speed will not work as it was part of the Cummins ECU system. If they had just amde their controller able to give engine rpms to the dash and trans controller and had the basic engine functions wired through it then you wouldn't need the Cummins controller on there at all.

NH CR920 and CR940 combines had an P series pump with Bosche's electric actuator built in it. It worked very fast on throttle response. I can see with a normal liniar actuator why throttle lever response would be a bit slow.